The present invention relates to superabsorbent materials and compositions containing superabsorbent materials exhibiting enhanced blood absorbence properties and methods for enhancing the blood absorbence properties of such superabsorbent materials and compositions. More specifically, the present invention relates to superabsorbent materials exhibiting enhanced blood absorbence properties for use in disposable, superabsorbent products such as feminine hygiene articles and medical articles.
Superabsorbent polymers have been developed in recent years that are capable of absorbing many times their own weight of liquid. These polymers, which are also known as water insoluble hydrogels, have been used to increase the absorbency of sanitary products, such as diapers and sanitary napkins. Superabsorbent polymers are often provided in the form of particulate powders, granules, or fibers that are distributed throughout superabsorbent cellulosic products to increase the absorbency of the product. Superabsorbent particles are described, for example, in U.S. Pat. No. 4,160,059; U.S. Pat. No. 4,676,784; U.S. Pat. No. 4,673,402; U.S. Pat. No. 5,002,814; and U.S. Pat. No. 5,057,166. Products such as diapers that incorporate superabsorbent hydrogels are shown in U.S. Pat. No. 3,669,103 and U.S. Pat. No. 3,670,731.
Superabsorbents have not found widespread use in superabsorbent sanitary articles, such as sanitary napkins, surgical wipes, and other articles used to absorb blood and other serous body fluids, because the superabsorbent materials do not absorb blood readily, nor do they have a high capacity for blood. The low blood absorbent capacity of the superabsorbent material means that large amounts of the superabsorbent material must be incorporated into blood absorbent articles, a factor which increases the production and materials cost for such superabsorbent articles.
U.S. Pat. Nos. 4,190,563 and 4,435,172 describe methods for improving the dispersability of particulate superabsorbent materials within blood. The ""563 patent describes improving blood dispersability of superabsorbent materials by surface treating the material with one or more high molecular weight polyethers. The ""563 patent describes that the polyethers can be used in amounts ranging from about 1% to about 35% by weight. The ""563 patent describes that the polyether coated superabsorbent materials exhibited improved dispersability in blood. The ""172 patent describes superabsorbent articles wherein the blood absorption rate is increased by the addition of amido compounds and non-ionic surfactants to water-soluble hydrophillic polymers. Such treated water-soluble hyrophillic polymers tend to be prone to potential risks of toxicity of the polymer and surfactants during use and after disposal (i.e., leaching of unused polymer or surfactant).
A superabsorbent for blood and serous body fluids is disclosed in U.S. Pat. No. 4,693,713. The disclosed superabsorbent composition includes component A, which is described as a water swellable synthetic or natural polymer or copolymer, and component B, which is described as an inorganic or organic compound that at normal temperature is present in the form of a pourable powder and is water soluble. The relatively high levels of component B described in the ""713 patent contribute to processing, handling, use (from a toxicity standpoint) and disposal problems.
U.S. Pat. No. 4,381,784 describes an superabsorbent article for absorbing blood that includes a water soluble blood gelling agent to thicken and bind menstrual fluid within the superabsorbent article. According to the ""784 patent, the blood gelling agents react with the protein present in blood or menstrual fluid, form particulate disordered structures according to the fourth class of gels defined by Flory, which are essentially completely water soluble, essentially completely linear, and which when placed in water will not form a Class 4 gel without the presence of blood protein. Such water soluble gelling agents are susceptible to the same risks as the water-soluble hydrophillic polymers discussed above with respect to the ""784 patent.
U.S. Pat. No. 5,241,009 describes polycarboxyl group containing superabsorbents wherein neutralization of said carboxyl groups with potassium or lithium is described as providing a polymeric composition specifically adapted to absorb proteinaceous fluids, such as blood.
It would be advantageous to provide a superabsorbent material and composition which can be used in sanitary superabsorbent articles, such as sanitary napkins, and surgical wipes, which have a blood absorbent capacity and blood retention properties that would make them suitable choices for improving the blood absorbency of such articles. It would further be advantageous to provide such superabsorbent materials in a manner that is compatible with existing methods of producing such materials and incorporating them into absorbent articles. It would also be advantageous to provide such superabsorbent materials that do not suffer from the drawbacks of prior materials for absorbing serious fluids, such as blood.
The foregoing and other advantages are provided by the superabsorbent materials and compositions and methods of producing the superabsorbent materials and compositions in accordance with the present invention. Applicants have found that certain of the binders described in the earlier filed applications referenced above, when combined with superabsorbent materials as described below, surprisingly enhance the blood absorbence properties of the superabsorbent material and compositions containing the superabsorbent material and enhancing agents. The advantages of the present invention are obtained by providing superabsorbent materials in combination with enhancing agents that enhance the blood absorbence properties such as free swell blood absorbent capacity and after load blood absorbent capacities, of the superabsorbent materials, and compositions containing the same.
In accordance with the present invention, the enhancing agents can be provided with the superabsorbent materials in several ways, e.g., at least partially coating the superabsorbent material with the enhancing agent, at least partially embedding the enhancing agent in the superabsorbent material, or providing a mixture of superabsorbent material and a fibrous material at least partially coated with the enhancing agent. The enhancing agents can be polymeric enhancing agents, non-polymeric organic enhancing agents, or nonreactive combinations thereof with each other.
In one aspect of the present invention, when the polymeric enhancing agent is to be applied to the superabsorbent material, it includes enhancing agent molecules that have at least one functional group capable of forming a hydrogen bond or a coordinate covalent bond with the superabsorbent material. The enhancing agent is applied to the superabsorbent material to at least partially coat the superabsorbent material, and/or partially embed the enhancing agent in the superabsorbent material, and enhance the blood absorbence properties, such as free swell blood capacity and after load blood capacity, of the superabsorbent material.
In a preferred embodiment of this aspect of the present invention, the polymeric enhancing agent is present in an amount ranging from about 0.01% to about 3% of the weight of the superabsorbent material; more preferably about 0.01% to about 1.0% and the free swell blood absorbent capacity of the treated superabsorbent material is preferably at least 1.15 times, and more preferably at least 1.5 times the free swell blood absorbent capacity of the untreated superabsorbent material. In another preferred embodiment, the after load blood absorbent capacity of the treated superabsorbent material is preferably at least 1.15, and more preferably 1.5 times the after load blood absorbent capacity of the untreated superabsorbent material.
In still another preferred embodiment of this aspect of the present invention, the superabsorbent material includes superabsorbent particles that can be combined with a fibrous material to form an superabsorbent web or pad.
In accordance with this aspect of the present invention, the superabsorbent material treated with enhancing agent can be shipped to distribution points (for example, a customer""s facility) where enhancing agent containing superabsorbent materials are further processed, e.g., combining with a fibrous material. Alternatively, the superabsorbent material treated with enhancing agent may be combined with a fibrous material by manufacturers of the fibrous material.
The polymeric enhancing agent may be selected from the group consisting of polyglycols [especially polyethylene glycol or poly(propyleneglycol)], a polycarboxylic acid, a polycarboxylate, a poly(lactone) polyol, such as diols, a polyamide, a polyamine, a polysulfonic acid, a polysulfonate and combinations thereof Specific examples of some of these enhancing agents, without limitation, are as follows: polyglycols include polypropylene glycol (PPG) and polyethylene glycol (PEG); poly(lactone) polyols include poly(caprolactone) diol; polycarboxylic acids include polyacrylic acid (PAA); polyamides include polyacrylamide or polypeptides; polyamines include polyethylenimine and polyvinylpyridine; polysulfonic acids or polysulfonates include poly(sodium-4-styrenesulfonate) or poly(2-acrylamidomethyl-1-propanesulfonic acid); and copolymers thereof (for example a polypropylene glycol/polyethylene glycol copolymer). The polymeric enhancing agent typically has repeating units. The repeating unit may be the backbone of a compound, such as with a polypeptide, wherein the repeating polyamides occur in the peptide chain. The repeating unit may also refer to units other than those in the backbone, for instance a repeating acrylic acid unit. In such a case, the repeating units may be the same or different. In accordance with this aspect of the present invention, when the enhancing agent is applied to the superabsorbent material, the polymeric enhancing agent has a functional group capable of forming a hydrogen bond or a coordinate covalent bond with the superabsorbent material, and optionally, when the superabsorbent material is to be combined with a fibrous material, a functional group capable of forming a hydrogen bond with the fibrous material and, thus, binding the superabsorbent material to the fibrous material. At this time, a most preferred polymeric enhancing agent is polyethylene glycol.
In accordance with this aspect of the present invention, the non-polymeric enhancing agent has a volatility less than water, a functional group that is capable of forming a hydrogen bond or coordinate covalent bond with the superabsorbent material, and preferably where the superabsorbent material is to be combined with and bound to a fibrous material, a functional group that is capable of forming a hydrogen bond with the fibrous material. The non-polymeric enhancing agent is an organic enhancing agent, and preferably includes, without limitation, a functional group selected from the group consisting of a carboxyl (for example, carboxylic acids), a carboxylate, a carbonyl (for example, aldehydes), a sulfonic acid, a sulfonamide, a sulfonate, a phosphoric acid, a phosphoramide, a phosphate, an amide, an amine, a hydroxyl (such as an alcohol) and combinations thereof (for example, an amino acid or an hydroxy acid), wherein there is at least one functionality on the molecule selected from this group. Examples of such enhancing agents include polyols, polyamines (a non-polymeric organic enhancing agent with more than one amine group), polyamides (a non-polymeric organic enhancing agent with more than one amide group), polycarboxylic acids (a non-polymeric organic enhancing agent with more than one carboxylic acid functionality), polyaldehydes (a non-polymeric organic enhancing agent with more than one aldehyde), amino alcohols, hydroxy acids and other enhancing agents. These enhancing agents have functional groups that are capable of forming the specified bonds with the superabsorbent material and, when necessary and preferred, with the fibrous material.
More preferably, the non-polymeric organic enhancing agent is selected from the group consisting of glycerin, a glyceride monoester, a glycerin diester, ascorbic acid, urea, glycine, ammonium citrate, taurine (2-aminoethanesulfonic acid), dipropylene glycol, p-aminosalicylic acid, sorbitol, lactic acid, and combinations thereof. The preferred enhancing agents are non-polymeric molecules with a plurality of hydrogen bonding functionalities. Particularly preferred enhancing agents include those that can form five or six membered rings, most preferably six membered rings, with a functional group on the superabsorbent material surface. At present, glycerin, sorbitol, lactic acid, and combinations thereof are a particularly preferred enhancing agents.
In accordance with the present invention, the superabsorbent material treated with the polymeric or non-polymeric enhancing agent may or may not be combined with and/or bound to the fibrous material, although it is preferred from the standpoint of retention of superabsorbent material within an superabsorbent article. The fibrous material that the superabsorbent material is combined with may be natural fibers, such as cellulosic fibers or synthetic fibers. In one preferred embodiment, an superabsorbent product formed in accordance with the present invention includes a fibrous cellulosic mat that contains superabsorbent hydrogel particles in particulate form at least partially coated with enhancing agent and/or with enhancing agent at least partially embedded in its structure. Other superabsorbent materials such as superabsorbent granules and superabsorbent fibers may benefit from the treatment of the present invention. The superabsorbent particles are capable of forming hydrogen bonds or coordinate covalent bonds with the enhancing agent. The amount of enhancing agent present typically depends on a number of factors, including the nature of the enhancing agent and the superabsorbent particles. Hence, one skilled in the art will realize that the enhancing agent and the amount of enhancing agent suitable and particularly useful for a particular application will vary. However, the non-polymeric enhancing agent may suitably be present in an amount of from about 0.01% to 10% of the total weight of the superabsorbent materials, preferably from about 0.01% to 3%, and more preferably about 0.01% to 1%. When the nonpolymeric enhancing agent is used in accordance with this aspect of the present invention, the free swell blood absorbent capacity of the treated superabsorbent material is preferably at least 1.2 times, and more preferably at least double the free swell blood absorbent capacity of the untreated superabsorbent material. In another preferred embodiment, the after load blood absorbent capacity of the nonpolymeric enhancing agent treated superabsorbent material is preferably at least 1.2 times, and preferably at least double the after load blood absorbent capacity of the untreated superabsorbent material. If the superabsorbent particles of the present invention are present in a fibrous superabsorbent structure, they will be present in an amount of about 0.05% to 80% of the total weight of the fibrous material and the particles, preferably 1% to 80% or 3% to 80%, or more than 3% by weight. A particularly suitable range of particles is 5% to 70% by weight of the fibrous material and particles. An example of a suitable superabsorbent particle is a superabsorbent polymer, such as a starch-graft polyacrylate hydrogel fine or larger size particle, such as a granule, which is capable of forming hydrogen bonds with the enhancing agent.
The enhancing agent can be applied to the superabsorbent material in a number of ways, for example, by spraying the enhancing agent or agents onto the superabsorbent materials or slurrying or immersing them in the enhancing agent.
In a second aspect of the present invention, a blood absorbent composition of fibrous material and superabsorbent material is provided wherein the fibrous material has been at least partially coated with an enhancing agent, wherein combining the enhancing agent coated fibrous material with a superabsorbent material enhances the blood absorbent properties of the superabsorbent material and mixture, e.g., free swell blood absorbent capacity and after load blood absorbent capacity. As with the first aspect of the present invention summarized above, the enhancing agent may be either polymeric or nonpolymeric in nature and includes enhancing agent molecules.
In accordance with this aspect of the present invention, the polymeric enhancing agent may be selected from the group of polymeric enhancing agents summarized above with respect to the aspect wherein an enhancing agent is applied to the superabsorbent material. The polymeric enhancing agent molecules useful in this aspect have at least one functional group capable of forming a hydrogen bond coordinate covalent bond with the superabsorbent material.
The non-polymeric enhancing agent useful for application to the fibrous material in accordance with this aspect of the present invention has a volatility less than water. Suitable non-polymeric enhancing agent molecules have at least one functional group that is capable of forming a hydrogen bond or coordinate covalent bond with the superabsorbent material. The non-polymeric enhancing agent is an organic enhancing agent, and includes those non-polymeric organic enhancing agents summarized above with respect to the aspect of the present invention wherein an enhancing agent is applied to the superabsorbent material.
More preferably, in accordance with this aspect of the present invention, the organic non-polymeric enhancing agent is selected from the group consisting of glycerin, a glycerin monoester, a glycerin diester, ascorbic acid, urea, glycerin, ammonium citrate taurine (2-aminoethanesulfonic acid), p-aminosalicylic acid, dipropylene glycol, sorbitol, lactic acid, and combinations thereof. In accordance with this aspect of the present invention, particularly preferred enhancing agents include those that can form five or six membered rings, most preferably six membered rings, with a functional group on or close to the superabsorbent material surface. At present, glycerin, sorbitol, lactic acid, and combinations thereof are particularly preferred, with glycerin being more particularly preferred.
The fibrous material useful in accordance with this aspect of the present invention may be natural fibers, such as cellulosic or synthetic fibers. It has been found that whether the enhancing agent treated fibrous material and the superabsorbent material are combined, the superabsorbent material exhibits blood absorbence properties that are enhanced, and accordingly the mixture of superabsorbent material and treated fibrous material exhibit blood absorbence properties that are enhanced compared to a mixture of untreated fibrous material and the superabsorbent material. Accordingly, a superior superabsorbent composition is produced that has improved blood absorbent properties, such as free swell blood capacity and after load blood capacity.
In one preferred embodiment of this aspect of the present invention, an absorbent product comprises a fibrous cellulosic mat that contains superabsorbent hydrogel particles in particulate form. The superabsorbent particles are capable of forming hydrogen bonds or coordinate covalent bonds with the enhancing agent, depending upon the enhancing agent, while depending on its functionality the enhancing agent may form hydrogen bonds with the hydroxyl groups of the cellulose fibers. The amount of enhancing agent present typically depends on a number of factors, including the nature of the enhancing agent and superabsorbent particles. Hence, one skilled in the art will realize that the amount of enhancing agent suitable and particularly useful for a particular application will vary. However, the enhancing agent may suitably be present in an amount of from about 2% to 30% of the total weight of the fibrous material and enhancing agent. An especially suitable range of enhancing agent is about 2% to 15% of the total weight of the fibrous material and enhancing agent. The superabsorbent particles may suitably be present in an amount of about 0.05% to 80%, preferably about 1% to 80% or about 3% to 80%, or more than about 3% by weight of the total weight of the fibrous material and the particles. A particularly suitable range of particles is about 5% to 70% by weight of the fibrous material and particles. An example of a suitable particle is a superabsorbent polymer such as a starch graft polyacrylate hydrogel fine or larger size particle such as a granule. In a preferred embodiment of this aspect of the present invention, the after load blood absorbent capacity of a mixture of enhancing agent treated fibrous material and superabsorbent particles is at least 1.3 times the after low blood absorbent capacity of a mixture of untreated fibrous material and superabsorbent particles.
In especially preferred embodiments of this aspect of the present invention, the fibers are cellulosic and the particles are superabsorbent particles. The fibers may also be continuous or discontinuous synthetic or natural fibers.
When the preferred liquid enhancing agent is used (for example, glycerin or a solution of glycine powder), the fibers suitably contain at least about 0.5% water by weight. A solid enhancing agent is suitably used with fibers having less than 0.5% water by weight if the enhancing agent is heated above its melting point to liquefy it. The solid can be applied to the fibers as a hot saturated solution or the solid enhancing agent may be heated above its melting point to liquefy the enhancing agent, which is later applied to the fibers. The enhancing agent may be thermoplastic or meltable, such that it can be heated above its melting point/or softening point and then cooled to fuse fibers to each other. The thermoplastic properties of the enhancing agent can also provide mechanical adherence between the particles and fibers.
The present invention also is directed to absorbent products produced by any of the methods described herein, and to absorbent articles comprised of such absorbent products.